The present disclosure relates to an organic EL display emitting light with use of electroluminescence (EL) effect, and a method of manufacturing the same.
As the development of information and communication industry is accelerated, display elements with higher performance are demanded. An organic EL element attracting attention as a next-generation display element has advantages of not only a wide viewing angle and excellent contract but also fast response time.
Materials of a light-emitting layer and the like forming the organic EL element are broadly divided into low-molecular materials and high molecular materials. It is generally known that the low-molecular materials exhibit higher light emission efficiency and a longer lifetime, and in particular, the low-molecular materials have high performance of emitting blue light.
Moreover, as a method of forming an organic film of the organic EL element, a film made of a low-molecular material is formed by a dry method (an evaporation method) such as a vacuum deposition method, and a film made of a high-molecular material is formed by a wet method (a coating method) such as a spin coating method, an ink jet printing method or a nozzle coating method.
The vacuum deposition method has an advantage that it is not necessary to dissolve a forming material of an organic thin film in a solvent, and it is not necessary to remove the solvent after film formation accordingly. However, in the vacuum deposition method, separate coating with use of a metal mask is difficult, and in particular, facility and manufacturing cost for forming large panels is high; therefore, the vapor deposition method has disadvantages that it is difficult to apply the vacuum deposition method to a large-screen substrate and mass production is difficult. Therefore, the ink-jet printing method or the nozzle coating method which relatively easily achieves an increase in area of a display screen attracts attention.
However, specifically blue light-emitting materials in high-molecular materials used in the ink-jet printing method or the nozzle coating method are not practical because the blue light-emitting materials have low light-emission luminance and low lifetime characteristics, and it is considered difficult to perform patterning of a blue light-emitting layer by the wet method.
Therefore, Japanese Unexamined Patent Application Publication No. 2006-140434 discloses a display formed by forming, as common layers, a blue light-emitting layer and subsequent layers, which have insufficient characteristics when being formed by the wet method, above a red light-emitting layer and a green light-emitting layer formed by the wet method including ink-jet printing. When the display has such a configuration, very fine pattering on the blue light-emitting layer is not necessary; therefore, there is a high possibility of achieving an increase in size of the display.